<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>会使用typepf关键字查看变量的类型</title>
</head>
<body>

</body>
</html>
<script>
    //boolean
    let l1=true;
    document.write(typeof (l1)+"<br>");
    let l2=null;
    document.write(typeof(l2)+"<br>");
    //undefined
    let l3;
    let l4=10;
    document.write(typeof (l4)+"<br>");

    let l5="hello";
    document.write(typeof(l5)+"<br>");
    let l6=100n;
    document.write(typeof(l6)+"<br>");

</script>